Thermo-electric pyrometer system.



R. P. BRUWN.

THERMO ELECTRIC PYRONIETER SYSTEM.

Patented June 29, 1915.

APPLICATION FILET) 0CT9, 1914.

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RICHARD P. BROWN, OF PHILADELPHIA, PENNSYLVANIA.

THERMO-ELECTRIC PYROMETER SYSTEM.

Specification of Letters Patent.

Patented June 29, i915.

Application led ctober 9, 1914. Serial No. 865,814.

T0 all whom it may concern Be it known that I, RICHARD P. BROWN, acitizen of the United States, and a resident of the city and county ofPhiladelphia, State of Pennsylvania, have invented certain new anduseful Improvements in Thermo-Electric Pyrometer Systems, of which thefollowing is a specification.

My invention relates to improvements in thermo-electric pyrometersystems and the object of my invention is to furnish an automatic meansfor maintaining the cold junction of one or more thermo-couples at acertain definite temperature, and also to furnish in connectiontherewith a means whereby an observer at a distance may be able at anytime to ascertain the temperature of the one or more cold junctionswithout the necessity of visiting the place where the cold junctions arelocated.

It is well known that a thermo-couple generates a voltage proportionalto the difference in temperature of the hot and cold junctions, and itis essential therefore that the cold junction be kept at a constant orknown temperature. This cold junction may be at some distance from thethermo-couple by using leads of similar materials to the thermo-coupleitself, in which case the cold junction is actually at the end of thesespecial leads.

It has been customary in using thermoelectric pyrometers to eitherassume or measure with a thermometer, the temperature of the coldjunction. This temperature liuctuates with atmospheric changes oftemperature and naturally in the vicinity of furnaces operating at hightemperatures, these changes of temperature may amountv to 100 degrees ormore. The cold junction temperature, having been determined, the pointeron the indicating or recording instrument is set vto the temperature ofthe cold junction, say 75 Fahr., when the instrument will readcorrect/ly just as long as the temperature of the cold junction remainsconstant.

My invention consists of a boX or case in which a constant temperaturecan be maintained by means of a thermostat and ordinary incandescentlamp, the thermostatic strip of metal in contracting when thetemperature fallsbelow the desired point, completing an electricContact, the circuit being closed and the lamp lighted. Heat given oil'by the lamp causes the tem erature to rise n the box and with a rise oone or two degrecs the contact is broken and the light is extinguished.The thermostat having been set to make Contact at say 1000, atemperature within one or two degrees of that point can be maintained.

The thermo-couples, of which there may be one or more for indicating orrecording the temperature of a furnace or furnaces, are of the usualwell known construction, their hot junction being adapted for subjectionto heat and the cold junction located within the box above described formaintaining the temperature o'f the cold junction of each thermo-coupleat a constant temperature. One of these boxes which we may call thecompensating box may be used with each thermo-couple, or the coldjunctions from several thermo-couples may be brought to the one box byusing compensating leads composed of the same material as thethermo-couples to transfer the cold juntion to the end of` thesecompensating eac s.

rFhe compensating box is usually located near the place or places wherethe temperature is to be measured and from this compensating box are runcopper wires to the instrument, frequently located at some distance, onwhich the temperature is indicated or recorded by the well known formof' millivoltmeter. lV here more than one thermo-couple is used a switchis installed beside the instrument to permit of selectively connectingthe various thermo-couples to the instrument.

In order that the operator of the instrument may know the cold junctiontemperature in the compensating box without the necessity of visitingthis box to observe the temperature ou the thermometer mounted therein,I install a thermo-couple in the compensating box and carry the coldjunction of this thermo-couple to the indicatin or recording instrument,connecting pre erably one side of the line through a point on the switchboard which can be marked test A thermometer should be preferablymounted on or be adjacent to the in dicating or recording instrument.

The operation of the system is as follows The operator observes thetemperature of the thermometer at the indicating or recordinginstrument, we will assume this temperature to be 75o I?. He thenadjusts the pointer by the zero adjusting device on the instrument to 75on the scale. He

-now closesi the switch connecting the test thermo-couple in thecompensating box to the instrument and we will assume that the pointermoves up to 100. This shows that the temperature of the compensating box and that of the cold junctions of the various thermo-couples is 1000.The switch is thrown oi and he now adjusts the pointer by the zeroadjusting device to 1000, the actual cold junction temperature. Thetemperature can then be read on the thermocouple or couples in servicewith precision.

My invention is illustrated in the accompanying drawings which form partof this specification, in which similar letters of reference indicatesimilar parts throughout the several views, and in which Figure 1, is adiagrammatic view of my thermo-electric pyrometer system, and Fig. 2, afront elevation of the box for inclosing the cold junctions of thethermo-couples, its front being removed to show the means formaintaining its interior at a constant temperature.

Referring to Fig. 1, 8 and L1 are thermocouples of usual constructionthe cold junctions 5-6 of which are placed in a closed box 7. 8 is anindicating or recording'instrument ot' well known construction which issituated at a distance, possibly several hundred feet, from the box 7.r1`his instrument is fitted with the usual scale 9, pointer 10 andbinding posts 11-12 To one of the binding posts, as 11, are connectedthe copper leads 13-15 connected respectively to one side of the coldjunctions 5 and 6 of the thermo-couples 8 1. The leads 14-16 connectedto the other side ot these cold junctions being connected, respectively,to points a and Z which, through a switch 17, may be connected one at atime, to a wire 18 which is connected to the binding post 12 of theindicating or recording instrument.

19 is an incandescent lamp, Fig. 2, inside of box 7 one of the linewires 20 of which is connected with a stop 21 adapted to be engaged byan: arm 28 of a thermostatic coil 22. The stop 21 is carried upon atoothed segment 24 which is pivoted at 25. 26 is a toothed segmentmeshing with segment 24 and byl rocking this latter segment the formerone may' be moved so as to move the stop 21 toward or away from arm Apointer 27 carried by the pivot which carries segment 26, operating inconnection with a fixed scale 28 will show the position of segment 20and this scale may be marked so as to indicate degrees oi. temperature.The stop 21, the coil 22, and arm 23 being set so that at a giventemperature, say 100, the expansion of coilv22 will move arm 28 out ofcontact with stop 21 the lamp 19 will be extinguished whenever thistemperature is reached and will be rie-lighted whenever the temperaturefalls below this limit. 1n

practice the device willmaintain the desired temperature within one ortwo degrees at all times.

A. thermometer 29 may be placed within box 7to show the temperaturetherein but as it would be inconvenient to the operator or observer, whohas the indicating instrument 8 located at a distance, to visit the box7 to ascertain its temperature, l place within it an auxiliarythermo-couple 30 one of the compensating leads 31 of which is connectedto the binding post 11 of the indicating instrument and the other, 82,to the test point p which, through switch 17 and wire 18, may beconnected to binding post 12 of instrument 8.

When about to read on the instrument 8 the temperature of anyone of thethermocouples 3 4, the observer first assures himself of the temperatureof the room in which the instrument 8 is placed, this he does by anordinary thermometer 33 near instrument 8. `We will assume thistemperature is 75O,which therefore is the temperature of the coldjunction of the auxiliary thermocouple 30, and the pointer 10 ofinstrument 8 will be set by the observer at 75O on scale 9. He now movesswitch 17 to contact with test point p when the pointer 10 will move upto the temperature within box 7, say 1000, when the pointer is set tothis temperature by the zero adjuster with which most millivolt metersare furnished, it being necessary and well known that the pointerinitially should be set at the temperature of the cold junction of thethermo-couple. The pointer having been set at the cold junctiontemperature the switch is moved to one'of the points a, Zi, etc.,completing upon contact with one offthese points the circuit from someone of the thermo-couples to and through instrument 8 upon'the scale 9of which will be indicated by pointer 10 the degrees of temperaturecorresponding with the current generated by the couple.

r1`here may be as many separate couples used as may be desired one ofthe leads from each couple being connected to one of the binding postsof the instrument 8 and the other lead to its own point a, b, etc.,which through switch 17 and wire 18 can be selectively connected to theother binding post of the instrument 8.

Having thus described myinvention 1 cla-im as new and desire to secureby Letters Patent 1. A. thermo-electric pyrometer system comprising, incombination, an indicating instrument, a thermo-couple, an inclosedchamber in which is situated the cold junction of said couple, leadsconnecting said thermo-couple through a switch with said indicatinginstrument, said switch, a thermostatioally controlled meansfor'maintaining said chamber at a substantially uniform' temperature,and an auxiliary thermocouple the hot junction of Which is Within saidchamber and the leads of which are connected through said switch withsaid indicating instrument.

2. A thermo-electric pyrometer system comprising, in combination, anindicating instrument, a thermo-couple, an inclosed chamber in Which thecold junction of said couple is placed, leads detachably connecting thecold junction of said couple and the binding posts of said indicatinginstrument,

an auxiliary thermo-couple the hot junction' of which is Within saidinclosed chamber and the leads of Which are adapted to be detachablyconnected to the 'binding posts of said indicating instrument, and athermostatic controlled means for maintaining said inclosed chamber at asubstantially constant temperature.

3. A thermo-electric pyrometer system comprising in combination, anindicating instrument, a thermo couple, an inclosed chamber in which issituated the cold junction of said couple, leads detachably connectingthe cold junction of said couple and the binding posts of saidindicating instrument, an auxiliary thermo-couple the hot junction ofWhich is situated Within said inclosed chamber, leads detachablyconnecting said auxiliary thermo-couple and the binding posts of saidindicating instrument, an electric lamp Within said inclosed chamber,and a thermostat-Within said chamber forming part of one of the lineWires of said c lamp and consisting of a thermostatic coil, an armcarried by said coil, a stop adapted to be engaged by said arm, and ameans for adjustably carrying said stop, all substantially as set forth.

RICHARD P. BROWN. Witnesses:

ROBERT A. ADAMS, JOHN P. GREEN.

